Area sensitivity of North American grassland birds is a significant conservation concern; yet, its causes are not known. I used point count data from 20 tall-grass prairie patches in Southern Manitoba to assess the relative importance of patch size, edge proximity, and landscape composition on the densities and species richness of grassland songbirds. The degree to which the landscape surrounding point count plots was open, as opposed to forested or urban, had a positive effect on species richness and the densities of most focal species, and was more important than patch size, edge proximity, or habitat amount. These results suggest that landscape openness, not patch size (with which it is usually correlated) drives area sensitivity. Small grassland patches embedded in open landscapes are less susceptible to area sensitivity and may be of high conservation value for grassland birds. / February 2017

The purpose of the present study was to investigate how plant spatial patterns and insect behavior interact to influence the population dynamics of insects using the plants. The study included three phases: l) field experiments using collards (Brassica oleracea) and the crucifer insect fauna; 2) simulation models representing the population dynamics of an insect herbivore as functions of insect dispersal behavior and host plant patch size; and 3) model-field syntheses integrating model predictions and field variability estimates to choose an appropriate spatial scale for future field experiments or applications. In field experiments on surrounding plant type, collards were planted with 1) other collards; 2) collards treated with a systemic insecticide; 3) broccoli, a related host; and 4) tomatoes, an unrelated host whose odor may repel crucifer pests. In three such experiments, eggs and larvae of the imported cabbageworm (Pieris rapae (L.)) were most abundant an collards surrounded by tomatoes. These results were contrary to those from previous experiments with other crucifer pests, but can perhaps be explained by P. rapae's preference for ovipositing on isolated host plants. In three patch size experiments, P. rapae eggs and larvae were more abundant on collards in small patches; in one of these experiments, the diamondback moth (Plutella xylostella (Linn.)) was more abundant in large patches. The results for P. rapae were consistent with previous studies showing more oviposition on plants in smaller patches and on plants at the edge of a patch. The simulation models predicted mean level and variability of an insect herbivore population based on interactions between insect behavior and host plant patch size. Features of insect behavior modeled were: 1) an inverse relationship between distance and dispersal; 2) preferences for host vs. nonhost plants, which differ for generalist and for specialist herbivores; and 3) preference of specialists for larger areas of host plants. Aspects of plant pattern studied were size and number of host plant patches in a background of nonhost vegetation. Constant, exponential and logistic growth of insect populations in the nonhost background and in the host patches were used. The models were designed to provide a theoretical framework for studying interactions between insect behavior and plant pattern, not to duplicate the dynamics of the field system. However, for the model-field syntheses, parameters of one model were fit to field data to establish a correspondence between expected differences in population levels predicted by the model and variability estimates obtained in the field experiments. The fitted model was used to construct a graph of differences in population levels versus patch size. Field variability estimates were used to calculate the least difference in population levels, for a given number of replicates and subsamples, that could be detected in field experiments. The least difference was compared with the differences predicted b y the fitted model to determine what patch sizes will produce significant effects of patch size on insect populations. This method was used to assess feasibility of future field experiments and to select appropriate patch sizes. The method can also be used to evaluate crop field size in agroecosystems as a component of pest management.

Habitat fragmentation and isolation can result in decreased occupancy and reproductive success within songbirds, particularly for species inhabiting urban environments where suitable habitat may be limited. The golden-cheeked warbler (Setophaga chrysoparia) is a federally endangered songbird that inhabits oak-juniper (Quercus spp.- Juniperus spp.) across central Texas. Past research on this warbler has indicated decreased patch occupancy near urban areas and negative reproductive effects associated with decreased distance to edge and decreased canopy cover. A rural study indicated warblers occupy patches ≥3 ha, and warblers in patches ≥20 ha are more likely to successfully fledge young. There are no thresholds yet identified for this warbler within urban environments, where effects of habitat fragmentation on reproductive success are more pronounced than within rural environments. I monitored patch occupancy, territory establishment, pairing success, and fledging success of warblers in an urban environment. I determined minimum patch-size thresholds for productivity measurements, and also monitored effects on productivity from canopy cover, woodland composition, distance to and size of the nearest habitat patch, and distance to the nearest habitat patch >100 ha. I compared my results to those from a similar study conducted in a rural system. I compared territory size and territory density between an urban and rural system. Warblers occupied 24% (n = 63) patches surveyed; the smallest patch occupied was 3.5 ha. The smallest patch with an established territory was 10.7 ha, and 10% (n = 63) of habitat patches had at least one established territory. Warblers successfully fledged young in 3 patches, the smallest of which was 26.5 ha. I found patch-size was predictive for territory establishment and pairing success with warblers requiring 13 ha (95% CI: 10.0 – 16.8 ha) and 19 ha (95% CI: 15.7 – 22.6 ha) habitat patches, respectively. I found a minimum threshold of approximately 66% canopy cover (95% CI: 65.2 – 66.4%) required for patch occupancy, and found no warblers established a territory in a habitat patch >25 m from the next nearest patch. I found higher minimum thresholds within an urban system for territory establishment and pairing success than those seen within a rural system. I suggest preserving warbler habitat patches >22 ha that are in close proximity to other habitat patches. This will help to enhance warbler habitat within urban areas and maintain reproductively viable habitat patches, while not halting development completely.

No description available.

Thesis (M.S.)--Miami University, Dept. of Zoology, 2005. / Title from first page of PDF document. Includes bibliographical references (p. 31-35).

<p>There has been a long-term decline in number of cyclic vole populations in boreal Sweden since the 1970s. Several hypotheses have been suggested to explain this decline. Commonly for <i>C. glareolus</i>, <i>C. rufocanus</i> and <i>M. agrestis</i>, the decline has followed upon an increased frequency and severeness of winter declines and has shown up as a drop in spring densities. The spring decline is most pronounced for <i>C. rufocanus</i>. In contrast to other voles, <i>C. rufocanus</i> also show a decline in fall densities, suggesting some additional disturbance in this species. Habitat fragmentation has been suggested as such an additional disturbance and in this thesis the effect of habitat fragmentation on <i>C. rufocanus</i> is explored.</p><p>At first the sampling method was evaluated i.e. whether the decline could be due to destructive sampling when the method in use in the long-term monitoring is snap-trapping. This resulted in a rejection of the destructive sampling hypothesis as a possible cause behind the decline in <i>C. rufocanus</i>. Habitat preference revealed that three habitats at the local scale (trap station) were high quality habitats for <i>C. rufocanus</i>: forest of moist and wet/hydric dwarf-shrub type, in addition to forest/swamp complexes rich in dwarf-shrubs. The occurrence of <i>C. rufocanus</i> at the landscape scale was positively correlated with the amount of boulder fields and a low degree of fragmentation of old-growth pine forests. There was considerable local variation in the decline in vole density among the 58 1-ha sampling plots, with respect to both density and timing of the decline, which suggested that habitat destruction outside sampling plots might be involved. Overall, clear-cuts had a negative influence on vole densities at both the local and landscape scale. A multiple regression analysis suggested that having both a high quality habitat at the local scale and a high proximity among xeric-mesic mires and a low connectivity among clear-cuts at the landscape scale were important for the occurrence of <i>C. rufocanus</i>.</p><p>Initial analysis at the landscape scale were based on landscape data collected from 2.5 x 2.5 km areas centred on the individual vole sampling plots. Further investigations, however, on the patch level suggest that focal forest patch size and quality was of major importance in determining occurrence and persistence of <i>C. rufocanus</i>. Although not tested formally in these studies, the habitat fragmentation hypothesis has so far received support. Currently <i>C. rufocanus</i> seems to be affected negatively by too low patch sizes of suitable habitats in the surrounding landscape suggesting that the amount of suitable habitats could already be below the fragmentation threshold. However, this has to be evaluated further. Work is in progress to establish time-series over local landscape changes, and to evaluate if such changes have been associated with local declines of <i>C. rufocanus</i> and whether habitat loss, true habitat fragmentation or both have been influential.</p>

There has been a long-term decline in number of cyclic vole populations in boreal Sweden since the 1970s. Several hypotheses have been suggested to explain this decline. Commonly for C. glareolus, C. rufocanus and M. agrestis, the decline has followed upon an increased frequency and severeness of winter declines and has shown up as a drop in spring densities. The spring decline is most pronounced for C. rufocanus. In contrast to other voles, C. rufocanus also show a decline in fall densities, suggesting some additional disturbance in this species. Habitat fragmentation has been suggested as such an additional disturbance and in this thesis the effect of habitat fragmentation on C. rufocanus is explored. At first the sampling method was evaluated i.e. whether the decline could be due to destructive sampling when the method in use in the long-term monitoring is snap-trapping. This resulted in a rejection of the destructive sampling hypothesis as a possible cause behind the decline in C. rufocanus. Habitat preference revealed that three habitats at the local scale (trap station) were high quality habitats for C. rufocanus: forest of moist and wet/hydric dwarf-shrub type, in addition to forest/swamp complexes rich in dwarf-shrubs. The occurrence of C. rufocanus at the landscape scale was positively correlated with the amount of boulder fields and a low degree of fragmentation of old-growth pine forests. There was considerable local variation in the decline in vole density among the 58 1-ha sampling plots, with respect to both density and timing of the decline, which suggested that habitat destruction outside sampling plots might be involved. Overall, clear-cuts had a negative influence on vole densities at both the local and landscape scale. A multiple regression analysis suggested that having both a high quality habitat at the local scale and a high proximity among xeric-mesic mires and a low connectivity among clear-cuts at the landscape scale were important for the occurrence of C. rufocanus. Initial analysis at the landscape scale were based on landscape data collected from 2.5 x 2.5 km areas centred on the individual vole sampling plots. Further investigations, however, on the patch level suggest that focal forest patch size and quality was of major importance in determining occurrence and persistence of C. rufocanus. Although not tested formally in these studies, the habitat fragmentation hypothesis has so far received support. Currently C. rufocanus seems to be affected negatively by too low patch sizes of suitable habitats in the surrounding landscape suggesting that the amount of suitable habitats could already be below the fragmentation threshold. However, this has to be evaluated further. Work is in progress to establish time-series over local landscape changes, and to evaluate if such changes have been associated with local declines of C. rufocanus and whether habitat loss, true habitat fragmentation or both have been influential.

In this dissertation, we are interested in the dynamics of spatially distributed populations. In particular, we focus on persistence conditions and minimal traveling periodic wave speeds for stage-structured populations in heterogeneous landscapes. The model includes structured populations of two age groups, juveniles and adults, in patchy landscapes. First, we present a stage-structured population model, where we divide the population into pre-reproductive and reproductive stages. We assume that all parameters of the two age groups are piecewise constant functions in space. We derive explicit formulas for population persistence in a single-patch landscape and in heterogeneous habitats. We find the critical size of a single patch surrounded by a non-lethal matrix habitat. We derive the dispersion relation for the juveniles-adults model in homogeneous and heterogeneous landscapes. We illustrate our results by comparing the structured population model with an appropriately scaled unstructured model. We find that a long pre-reproductive state typically increases habitat requirements for persistence and decreases spatial spread rates, but we also identify scenarios in which a population with intermediate maturation rate spreads fastest. We apply sensitivity and elasticity formulas to the critical size of a single-patch landscape and to the minimal traveling wave speed in a homogeneous landscape. Secondly, we use asymptotic techniques to find an explicit formula for the traveling periodic wave speed and to calculate the spread rates for structured populations in heterogeneous landscapes. We illustrate the power of the homogenization method by comparing the dispersion relation and the resulting minimal wave speeds for the approximation and the exact expression. We find an excellent agreement between the fully heterogeneous speed and the homogenized speed, even though the landscape period is on the same order as the diffusion coefficients and not as small as the formal derivation requires. We also generalize this work to the case of structured populations of n age groups. Lastly, we use a finite difference method to explore the numerical solutions for the juveniles-adults model. We compare numerical solutions to analytic solutions and explore population dynamics in non-linear models, where the numerical solution for the time-dependent problem converges to a steady state. We apply our theory to study various aspects of marine protected areas (MPAs). We develop a model of two age groups, juveniles and adults, in which only adults can be harvested and only outside MPAs, and recruitment is density dependent and local inside MPAs and fishing grounds. We include diffusion coefficients in density matching conditions at interfaces between MPAs and fishing grounds, and examine the effect of fish mobility and bias movement on yield and fish abundance. We find that when the bias towards MPAs is strong or the difference in diffusion coefficients is large enough, the relative density of adults inside versus outside MPAs increases with adult mobility. This observation agrees with findings from empirical studies.

In dieser Arbeit wurde der Frage nachgegangen, inwieweit sich die Habitatansprüche von drei Brutvogelarten, der Offenlandart Feldlerche (Alauda arvensis), der Heckenart Neuntöter (Lanius collurio) und der Waldart Schwarzspecht (Dryocopus martius), mit Landschaftsstrukturmaßen darstellen lassen, und ob sich Landschaftsstrukturmaße für die Habitatmodellierung eignen. Basis für die Berechnung der Landschaftsstrukturmaße ist ein Flächenschema des IÖR-Monitors aus dem Jahr 2013, welches aus Daten des AFIS-ALKIS-ATKIS-Modells (AAA-Modells) aufgebaut wurde. Dieses Schema bietet redundanzfreie Flächennutzungsdaten für ganz Deutschland. Da es nur flächenhafte Elemente enthielt, wurde es um gepufferte linienhafte Elemente, genauer um Hecken, Baumreihen und Feldwege ergänzt. Die Artdaten stammen aus dem Monitoring häufiger Brutvögel (MhB), ebenfalls aus dem Jahr 2013. Die Berechnungen der Landschaftsstrukturmaße wurden mittels ArcGIS-Modellen durchgeführt. Für die Feldlerche und den Schwarzspecht wurden die Landschaftsstrukturmaße Mean Shape Index (MSI), Mean Patch Size (MPS), Anteil geeigneter Habitate (Percentage of Landscape, PLand), Total Core Area (TCA), Fläche geeigneter Biotope ohne anthropogene Störeinflüsse (Fl_ungest) und die Kantendichte der Landschaft (Edge Density, ED) berechnet. Für den Neuntöter sind es MSI, MPS, PLand, Fl_ungest, die Kantendichte und die Fläche geeigneter Gehölzbiotope und Hecken. Es wurde aufgezeigt, dass teilweise höchst signifikante lineare Zusammenhänge zwischen dem Vorkommen der drei Arten und den Landschaftsstrukturmaßen existieren. Die damit erklärten Streuungen der Brutpaarzahlen sind allerdings relativ gering. Das Bestimmtheitsmaß B oder R² der Regressionsgeraden beträgt für die Feldlerche maximal 0,285 bei der Fläche ungestörter Habitate, für den Schwarzspecht maximal 0,332 bei dem Anteil geeigneter Habitate und beim Neuntöter lediglich 0,038, ebenfalls für die Fläche ungestörter Habitate. Der Grund hierfür ist, dass die Arten Ansprüche an die Habitate stellen, die sich nicht mit Landschaftsstrukturmaßen erklären lassen. Die Modelle der multiplen linearen Regression sind ungeeignet, um Brutpaarzahlen der Arten vorherzusagen. Ohnehin war es nur für die Feldlerche möglich, ein solches Modell zu erstellen, das höhere Bestimmtheitsmaße aufweist als die einzelnen Landschaftsstrukturmaße. Deutlich bessere Ergebnisse wurden mit einem Modell erzielt, das die Eignung der Landschaft und ihrer Struktur als Habitat anhand einer Bewertungsmatrix beurteilt. Hier wurde bestimmt, wie hoch der Anteil besetzter Untersuchungsflächen an der Gesamtzahl von Untersuchungsflächen einer bestimmten Gesamtpunktzahl ist. Die Zusammenhänge zwischen Punktzahl und Anteil besetzter Flächen wurde mit teils nichtlinearen Regressionsfunktionen dargestellt. Der Anteil erklärter Abweichungen (R²) beträgt bei der Funktion der Feldlerche 97,1%, der des Schwarzspechts 88,5% und der des Neuntö-ters 49,3%.

In dieser Arbeit wurde der Frage nachgegangen, inwieweit sich die Habitatansprüche von drei Brutvogelarten, der Offenlandart Feldlerche (Alauda arvensis), der Heckenart Neuntöter (Lanius collurio) und der Waldart Schwarzspecht (Dryocopus martius), mit Landschaftsstrukturmaßen darstellen lassen, und ob sich Landschaftsstrukturmaße für die Habitatmodellierung eignen. Basis für die Berechnung der Landschaftsstrukturmaße ist ein Flächenschema des IÖR-Monitors aus dem Jahr 2013, welches aus Daten des AFIS-ALKIS-ATKIS-Modells (AAA-Modells) aufgebaut wurde. Dieses Schema bietet redundanzfreie Flächennutzungsdaten für ganz Deutschland. Da es nur flächenhafte Elemente enthielt, wurde es um gepufferte linienhafte Elemente, genauer um Hecken, Baumreihen und Feldwege ergänzt. Die Artdaten stammen aus dem Monitoring häufiger Brutvögel (MhB), ebenfalls aus dem Jahr 2013. Die Berechnungen der Landschaftsstrukturmaße wurden mittels ArcGIS-Modellen durchgeführt. Für die Feldlerche und den Schwarzspecht wurden die Landschaftsstrukturmaße Mean Shape Index (MSI), Mean Patch Size (MPS), Anteil geeigneter Habitate (Percentage of Landscape, PLand), Total Core Area (TCA), Fläche geeigneter Biotope ohne anthropogene Störeinflüsse (Fl_ungest) und die Kantendichte der Landschaft (Edge Density, ED) berechnet. Für den Neuntöter sind es MSI, MPS, PLand, Fl_ungest, die Kantendichte und die Fläche geeigneter Gehölzbiotope und Hecken. Es wurde aufgezeigt, dass teilweise höchst signifikante lineare Zusammenhänge zwischen dem Vorkommen der drei Arten und den Landschaftsstrukturmaßen existieren. Die damit erklärten Streuungen der Brutpaarzahlen sind allerdings relativ gering. Das Bestimmtheitsmaß B oder R² der Regressionsgeraden beträgt für die Feldlerche maximal 0,285 bei der Fläche ungestörter Habitate, für den Schwarzspecht maximal 0,332 bei dem Anteil geeigneter Habitate und beim Neuntöter lediglich 0,038, ebenfalls für die Fläche ungestörter Habitate. Der Grund hierfür ist, dass die Arten Ansprüche an die Habitate stellen, die sich nicht mit Landschaftsstrukturmaßen erklären lassen. Die Modelle der multiplen linearen Regression sind ungeeignet, um Brutpaarzahlen der Arten vorherzusagen. Ohnehin war es nur für die Feldlerche möglich, ein solches Modell zu erstellen, das höhere Bestimmtheitsmaße aufweist als die einzelnen Landschaftsstrukturmaße. Deutlich bessere Ergebnisse wurden mit einem Modell erzielt, das die Eignung der Landschaft und ihrer Struktur als Habitat anhand einer Bewertungsmatrix beurteilt. Hier wurde bestimmt, wie hoch der Anteil besetzter Untersuchungsflächen an der Gesamtzahl von Untersuchungsflächen einer bestimmten Gesamtpunktzahl ist. Die Zusammenhänge zwischen Punktzahl und Anteil besetzter Flächen wurde mit teils nichtlinearen Regressionsfunktionen dargestellt. Der Anteil erklärter Abweichungen (R²) beträgt bei der Funktion der Feldlerche 97,1%, der des Schwarzspechts 88,5% und der des Neuntö-ters 49,3%.